Free space optics (FSO) is a telecommunication technology that uses light propagating in free space to transmit data between two points. The technology can be useful where the physical connection of the transmit and receive locations is difficult. For example, in cities, the laying of fiber optic cables can be expensive and, in some instances, impractical based upon the infrastructure already built.
Free space optics can also be used to communicate between spacecraft, since outside of the atmosphere there is little to distort the signal. In some instances, the optical links use infrared laser light. Communication is also possible using light emitting diodes (LEDs) or other light sources, in some systems.
The beams of light in FSO systems are transmitted by light focused on receivers. These receivers can, for example, be telescopic lenses able to collect the photon stream and transmit digital data.
The data can be any item of information that can be transmitted on a communication system. For example, types of data can include one or more application programs (i.e., sets of executable instructions), files to be executed by such programs, or data, among other types. Files to be executed can, for example, take the form of Internet messages, video images, radio signals, or computer files, among other items.